I have book catagories for Technical, Craft & Hobbies, Non-English, Fiction, Cookbooks and Other.

Technical catagory has textbooks as well as some how-to's, mainly the hi-tech stuff.
Craft & Hobbies catagory has (big surprise) craft and hobby books. Lots of how-to books, collecting, gardening etc.
Fiction and Cookbook catagories should be self-explanatory.
Non-English catagory is for books that are in other languages, or in multiple languages. Some have English too, not all though.
The Other catagory has anything else that doesn't fit in the other ones; a mixed bag.